From time to time during the last two years brief accounts of a remarkable series of vertebrate remains, from the Middle and Upper Eocene of the Fayûm district of Egypt, have been published in the pages of this Magazine. The species hitherto described include a number of highly interesting animals, but of the most extraordinary of all, viz. Arsinöitherium Zitteli, no figure has yet appeared in this Journal. We are therefore glad to take the opportunity of remedying this omission by availing ourselves of the kind permission of the Editor of The Sphere to reproduce two photographs of the skull of this animal, which appeared in the pages of that journal on September 12th, 1903, as illustrations of a short article by Professor E. Ray Lankester, which is the first account of Arsinöitherium published in this country, and from which some extracts are given below.